The invention relates to electronics and can be used in electronic units intended for reception and processing of the signals of satellite radio navigational systems (SRNS).
A specific feature of the design of electronic units used for reception and processing of SRNS signals is that they have to be incorporated into different functional devices: analogue super high-frequency and high-frequency devices performing the processes of reception and conversion of SRNS signals, and various analog-digital and digital devices, such as correlators, synthesizers, synchronizers, processors performing the processes of correlation search, tracing and digital processing of the received signals. Onboard Devices of Satellite Radio Navigation, I. I. Kudryavtsev, I. N. Mishchenko, A. I. Volynkin et al. Edited by V. S. Shebashevich, Moscow, Transport, 1988, page 112, FIG. 47 and page 126, FIG. 64. Another specific feature consists in a different degree of integration of the electric components realizing the different functions mentioned above. For example, microcircuits using a small, average or large degree of integration can be used. In this connection, when such different functional units and elements are combined in a single, generally small-size structure, including such dissimilar units and elements for processing the signals, usually having different frequencies, a problem arises with their electromagnetic compatibility, and mutual effect on levels of spurious and induced interference.
One known technical solution to such a problem is the development of a multiunit (multicard) structure, where separate printed-circuit cards incorporate electronic components relating to close (homogeneous) functional groups and processing signals that are similar in type and frequency, as, for example, in the prior art structures. Onboard Devices of Satellite Radio Navigation, I. I. Kudryavtsev, I.N.Mishchenko, A. I. Volynkin et al. Edited by V. S. Shebashevich, Moscow, Transport, 1988, p. 112, FIG. 47, Patent of Russian Federation No. 2013897, H05 K 7/00, published on May 30, 1994. In this case, the problems of reducing the spurious and induced interference can be solved by rather a simple means based, for example, on intercard screening. However, this way is connected with an increase in dimensions of the structure to be developed.
When the size consideration is important, monoblock structures are used, where the heterogeneous functional units and elements are incorporated within the framework of a common design unit, i.e. printed-circuit card, for example, in an electronic unit of a receiver/processor of SRNS signals, as described in Onboard Devices of Satellite Radio Navigation, I. I. Kudryavtsev, I. N. Mishchenko, A. I. Volynkin et al. Edited by V. S. Shebashevich, Moscow, Transport, 1988, p. 132, FIG. 69. The problems originating from spurious and induced interference can be solved by well-known methods consisting in screening separate functional units with corresponding metal screens.
Additional measures for reducing the spurious and induced interference may include other useful designer""s technique, in particular, installation of additional external matching elements linking the printed-circuit components with the housing of the unit, for example, as in USSR Inventor""s Certificate No 1826853, 05 K 5/00, published on Nov. 20, 1996, in special arrangement of the signal conductors on the printed-circuit card, like, for example, in Patent of Russian Federation No 2047947, 05 K 1/02, published on Nov. 10, 1995. See, Patent of Russian Federation No. 2013897, H05 K 7/00, published on May 30, 1994, Lund P. Precision Printed-Circuit Cards. Design and Production. oscow, Energoatomizdat, 1983, p. 112-115. A special layout of grounding and power supply conductors, for example, as in Lund P. Precision Printed-Circuit Cards. Design and Production. oscow, Energoatomizdat, 1983, p. 113-114 can also be used. In so doing there is no solution common for solving the given problem in all cases and in each concrete case use is made of a set of designer""s tools ensuring the solution of the problem under particular conditions.
The selected prior art for the claimed electronic unit is the electronic unit described in Majorov S. A et al., Electronic Computers. Handbook on Design. Edited by S. A. Majorov, Moscow Sovetskoe Radio, 1975 (pp. 258-261, FIG. 12.2xe2x80x94prior art), p. 258-261, FIG. 12.2 consisting of a single-card structure. The electronic unit selected as a prior art is a multilayer printed-circuit card, in which the interlayer connections of printed conductors are carried out by means of metallized holes of the interlayer connections, in which the external conductive layers have conductors, bonding contact areas, and built-in electronic components, while the internal conductive layers have other conductors and metallized ground planes and power supply planes with windows around metallized holes of the interlayer connections which were not electrically connected with these planes. For example, for the case of a printed-circuit card with ten conductive layers, the ground plane and power supply plane are disposed in the fourth and fifth layers respectively.
The disposition of the ground and power supply planes in different conductive layers of the printed-circuit card in the prior art unit allows one to solve the problem of reducing the spurious and induced interference. Thus, the successful solution of this problem can be attained, if the unit includes homogeneous electronic components and the processed signals are close on frequency as, for example, in case of the digital computer.
The technical problem to be solved by the claimed invention consists in elimination by improved design the spurious and induced interference for a small-size electronic unit performing the function of a receiver/processor of the SRNS signals and made on one multilayer printed-circuit card carrying heterogeneous (analogue, analog digital, digital) functional electronic components having of a different degree of integration, and the frequency band of the signals processed and converted in the signal block ranges from thousands of megaherts at the input down to several hertz at the output.
Solving this problem allows the existing elemental base for design of small-size navigational receivers/processors intended for mass customers dealing with SRNS xe2x80x9cGLOSNASSxe2x80x9d and xe2x80x9cNAVSTARxe2x80x9d signals.
The essence of the invention is an electronic unit comprising a multilayer printed-circuit card, in which the interlayer connections of the printed conductors are carried out by means of metallized holes of interface connections, in which the external conductive layers have conductors, bonding contact areas and electronic components, while the internal conductive layers have conductors and metallized ground and power supply planes with windows around the metallized holes of interface connections which are not electrically connected with these planes. The electronic components and printed conductors of the card are grouped together in three serially located zones, first of which corresponds to the zone of allocation of the electronic components performing the analog conversion of signals from the satellite radio navigational systems; the second one corresponds to the zone of allocation of the electronic components realizing the analog-digital conversion of signals; and the third one corresponds to the zone of allocation of the electronic components performing the digital conversion of signals.
The electronic components are mounted on a printed-circuit card with six conductive layers. In the second internal conductive layer ground planes of each of the zones are formed. In the third conductive layer power supply conductors of the first and second zones and additional conductors of the third zone are formed. In the fourth conductive layer additional conductors of the first and second zones and a metallized power supply plane of the third zone are formed. In the fifth conductive layer a ground plane of the first zone and additional conductors of the second and third zones are formed. In such a case, the ground planes made in the second conductive layer of the card are interconnected by means of direct ground linking conductors located according to the layout of the linking signal conductors. Electric connections are made in the external first and sixth conductive layers of the card, with the first zone being surrounded along its perimeter by screening wires placed opposite to each other on the first and sixth conductive layers of the card. The screening wires are connected to each other and to the ground planes of the given zone in the second and fifth conductive layers of the card by means of metallized holes made in the interface connections to form a closed electric circuit. The screening wires have breaks for passing the respective linking signal conductors, the points of breaks of the screening wires in the first and sixth conductive layers of the card correspond to the continuous metallized portions of the ground planes in the second and fifth layers of the card.
In the claimed electronic unit the width of the ground linking conductors performing the interconnection of the ground planes in the second conductive layer of the card are selected to be not less than 1 mm.
In the claimed electronic unit the conductors intended for screening the corresponding linking signal conductor are placed at both sides thereof and are connected to the ground planes by means of the metallized holes of the interface connections made at least at the beginning and end of each screening wire to form a closed electric circuit, the distance between the metallized holes not exceeding 5 mm.
In the claimed electronic unit the width of the screening wires made along the perimeter of the first zone in the first and sixth conductive layers of the card is selected to be not less than 2 mm.
In the claimed electronic unit the distance between the metallized holes of the interface connections interconnecting the screening wires in the first and sixth conductive layers of the cards and to the ground planes in the second and fifth conductive layers of the card does not exceed 5 mm.